A Benny Benassi bass synth and much more

Plektron IrCab

This potentially useful freebie can host the many Impulse Responses (in WAV format) that are also freely available for download from the internet, potentially giving you access to a massive range of sounds (both of 'spaces' and classic bits of gear). It's available in mono and stereo versions.

Platinumears Fl4tt3ry

Fl4tt3ry is one of those plug-ins that's inspired by rather than modelled on a classic piece of gear - specifically, a nameless compressor. Its processing is described as "gentle" and "squashy" (and also flattering, presumably) and is intended primarily for use on busses. That said, you can try it on individual channels, too.

Fsynthz Sandra

Low resonant sweeps and drones are this synth's stock in trade, though thick polysynth chords, leads and basses are also claimed to be within its capabilities. There are various sound-shaping options, and tooltips should ensure that features are explained as you work.

NTS Audio Labs Benassi Bass

This might just be the first free synth to be based on (and named after) the sound of a specific artist: its sole purpose appears to be to give you the Benny Benassi bass sound. To this end, there are two sine/saw oscillators, a double saw oscillator, a resonant filter, reverb and a glide option. What's more, 32 presets are included.

Prodyon Phenome

An 8-layer/8-part multitimbral SoundFont player that gives you typical synth-like features such as filters, an ADSR envelope and arpeggiators. You can make individual settings for each layer (MIDI channel, volume, pan, mute etc) and there's full MIDI Learn functionality.

Tekky Synths VoCoGaTe Free

It may have been originally designed to process vocal samples with its pitch shifting and gating abilities, but Tekky Synths says that VoCoGaTe's purpose now is to help you create "infinite percussion variations". This free version (the full one costs €30) has no main detuner, no FX and only one active patch but is properly functional.

DSK Overture

DSK is attempting to put an orchestra in your DAW with this one: there are 40 symphonic instruments and a drum kit. The plug-in has a four-layer architecture; layers can be stacked or sent to different MIDI channels. A range of sound-shaping options is available to each layer.